Mr. Hirsch’s newfound popularity comes largely because of the Common Core, a set of learning goals for kindergarten through 12th grade that have been adopted by almost every state in the last few years.

Mr. Hirsch did not write the Common Core, but his curriculums — lesson plans, teaching materials and exercises — are seen as matching its heightened expectations of student progress. And philosophically, the Common Core ideal of a rigorous nationwide standard has become a vindication of Mr. Hirsch’s long campaign against what he saw as the squishiness — a lack of specific curriculums for history, civics, science and literature — in modern education.